The invention relates to a gas sensor comprising a carrier substrate having a top side and an underside, wherein a gas inlet for a measurement gas is formed at the underside and wherein an electrode structure with an electrolyte layer is arranged on the top side, wherein the carrier substrate has a porous region comprised of a porous material and the porous material forms diffusion openings that connect the underside to the top side.
WO 2012/071151 A1 discloses such a gas sensor, wherein the electrode structure is applied directly to a porous carrier substrate and wherein the porous carrier substrate, on its underside facing away from the electrode structure, is provided with a back plate in order to delimit the gas entrance into the carrier substrate to an access opening.
Gas sensors are also known in which, for the purpose of conducting gas through the carrier substrate from the underside to the top side, drilled holes are introduced into the carrier substrate.
It has been found that such drilled holes have the disadvantage that the electrolyte applied or a catalyst coating arranged between electrolyte and electrode structure can penetrate into the drilled holes and close them during the coating process or later. This can have the consequence that the measurement gas can no longer reach the electrode structure at the top side of the carrier substrate during operation, as a result of which a proper function of the gas sensor is no longer ensured.
It has furthermore been found that applying the electrode structure on a porous carrier substrate is technologically complex.